1. Field of the Invention
The present invention relates to an exit-structure, associated with an ozone-filter, of an ozone-exhaust duct incorporated in an electrophotographic image-forming apparatus, which may be constructed as a copier, a printer, a facsimile or the like.
2. Description of the Related Art
As is well known, the electrophotographic image-forming apparatus performs the processes of: electrically charging a surface of a photosensitive drum by a corona discharger; forming an electrostatic latent image the charged surface of the photosensitive drum by an optical writer such as a laser beam scanner; electrostatically developing the electrostatic latent image with developer, i.e. toner; electrostatically transferring the developed toner image to a recording paper by the corona discharger; and thermally fixing the transferred toner image on the recording paper.
The corona dischargers, used in the electrical-charging and electrostatic-transferring processes, produce ozone during electrical energization of the corona dischargers. Of course, since ozone is harmful to human health, the produced ozone should be eliminated so that the ozone cannot flow out of the electrophotographic image-forming apparatus.
Conventionally, to prevent the outflow of the ozone from the electrophotographic image-forming apparatus, the photosensitive drum and various elements (including the corona dischargers) associated therewith, are arranged in a semi-closed space, and an ozone-exhaust duct is laid so as to be in communication with the semi-closed space. An ozone-filter, which comprises, for example, activated charcoal, is detachably attached to an exit of the ozone-exhaust duct, and a fan is incorporated in the ozone-exhaust duct at a suitable location thereof. The fan is driven by an electric motor such that a negative pressure is produced in the semi-closed space, so that air containing ozone is sucked from the semi-closed space, and is then discharged outside through the ozone-exhaust duct. Of course, when the air containing ozone passes through the ozone-filter, the ozone is eliminated from the air, thereby preventing the outflow of the ozone from the electrophotographic image-forming apparatus.
The air, sucked from the semi-closed space, further contains paper dust particles derived from the recording paper, and toner particles derived from the toner developer used in the electrostatic-developing process. Especially, when a continuous type of recording paper is used in the electrophotographic image-forming apparatus, a large quantity of paper dust particles is produced in comparison with the use of cut sheet of paper as the recording paper, because the continuous type of recording paper has a plurality of perforated separation-lines from which paper dust particles are generated.
Of course, the dust particles, contained in the sucked air, are captured by the ozone-filter, and cause the premature obstruction of the ozone-filter. Thus, the ozone-filter must be frequently exchanged with a fresh ozone-filter before an effective elimination of the ozone from the air can be ensured.